Machida is one of the only guys that Rashad would not be able to out slowpace in a fight. Machida is super patient, is a precision striker and would confuse the hell out of Rashad I think. Liddell was a straight forward striker, Forrest was a brawling type striker, Machida doesn't stick around long enough to mix it up and get caught.
If they do hit the mat Machida is a legit black belt who trains with top level BJJ guys on a day to day basis.
I'm not saying Rashad couldn't KO Machida but if there is a guy out there that can make Rashad look stupid its gonna be Machida....oh ya and Anderson too (of course).